Tinted optical article are widely used to provide visual comfort for the wearer and to protect the eyes of a wearer by preventing UV radiations or high energy visible light from damaging the eyes.
For example, tinted optical articles such as sunglasses may be designed to provide UV protection by protecting the eyes against the harmful effects of UVA and UVB rays of light and to reduce glare.
However, sunglasses significantly decrease retinal exposure of the eyes to beneficial light of the visible spectrum.
Empirical proof has evidenced that human physiology and behavior are largely influenced by retinal illumination. The vertebrate retina is a light-sensitive tissue lining the inner surface of the eye. This tissue has four main layers from the choroid to the vitreous humour: the retinal pigment epithelium, the photoreceptor layer (including rods and cones), the inner nuclear layer with bipolar and amacrine cells, and finally, the ganglion cell layer which contains some intrinsically photosensitive ganglion cells (1 to 3% of retinal ganglion cells (hereinafter referred to as “ipRGCs”)). Neural signals initiate in the rods and cones, and undergo complex processing by other neurons of the retina. The output from the processing takes the form of action potentials in retinal ganglion cells, the axons of which form the optic nerve. Several important features of both visual perception and non-visual biological functions can be traced to the retinal encoding and processing of light.
In particular, it is well known that ipRGCs mediate the production of melatonin in the pineal gland. Their responses to light can alter the biological clock in the suprachiasmatic nucleus of the hypothalamus, affecting circadian rhythms.
IpRGCs influence also the regulation of several non-visual biological functions, including sleep, alertness, mood, headaches, pupillary reflex, reproduction, and immune function by absorbing beneficial blue-green wavelengths of light of the visible spectrum (hereinafter referred to as “chronobiological blue light”).
Proper modulation of chronobiological blue light is thus essential, notably for proper synchronization of chronobiological rhythms.
The attenuation of beneficial light of the visible spectrum induced by sunglasses may progressively have a detrimental effect on the biological, hormonal and behavioral functions entrained by retinal illumination. A daily repeated and abusively prolonged wearing of sunglasses may interfere with the circadian rhythm of the wearer. In long-term, that might induce, for example, sleep troubles, seasonal affective disorders, mood disorders.
Furthermore, by significantly attenuating light luminance, sunglasses increase the pupil diameter with a logarithmic trend. The increase in pupil diameter, which normally accompanies decrease of illumination, may enhance to some extent optical aberrations and thus may have a deleterious effect on visual acuity.
Furthermore, the increase in pupil diameter increases the energetic irradiance of non-filtered wavelengths reaching the retina, particularly the noxious blue-violet wavelengths.
To address these problems, proposals have been made to produce sunglasses providing an optical filter configured to selectively transmit light within the range of chronobiological blue light.
Three examples of such optical articles are shown in FIG. 1B. More precisely, FIG. 1B shows the transmission spectrums of three types of sunglasses of class 3 designed to transmit chronobiological blue light and the related tint defined in the CIELAB color space whereas FIG. 1A shows the transmission spectrum of a classic sunglass of class 3 and the related tint defined in the CIELAB color space
As illustrated in FIG. 1B, transmitting the range and amount of chronobiological blue light affects the color in which the optical article is perceived and the tint of the latter.
More precisely, the three sunglasses of FIG. 1B exhibit:                A photopic transmission Tv higher than the one of the classic sunglass of FIG. 1A;        a relative lightness L of the color higher than the one of the classic sunglass of FIG. 1A and a shift in the values of the two other chromatic coordinates a and b of the CIELAB color space.        
Such proposed sunglasses unacceptably lighten and exhibit cosmetically undesirable tint, making difficult the production of sunglasses fulfilling the required transmittance properties of class 3 or 4 sunglass lenses.
Accordingly, the present invention aims to overcome the aforementioned drawbacks of the prior art.